学习目的：1.使用来源库LitePal(使用ORM 对象关系映射)创建数据库 2. 升级数据库(litepal会自动保存更新前的数据) 3.使用LitePal添加数据
1.使用来源库LitePal
配置LitePal
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compile 'org.litepal.android:core:1.3.2'
配置litepal.xml文件
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10<litepal>
<dbname value="BookStore" ></dbname>
<version value="2" ></version>
<list>
<mapping class="com.example.litepaltest.Book"></mapping>
<mapping class="com.example.litepaltest.Category"></mapping>
</list>
</litepal>用面向对象思维实现建表功能（不用和SQL打交道）
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61import org.litepal.crud.DataSupport;
public class Book {//Book对应Book表
private int id;
private String author;
private double price;
private int pages;
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
this.author = author;
}
public double getPrice() {
return price;
}
public int getPages() {
return pages;
}
public void setPages(int pages) {
this.pages = pages;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public void setPress(String press) {
this.press = press;
}
}将Book类映射到模型列表中
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10<litepal>
<dbname value="BookStore" ></dbname>
<version value="2" ></version>
<list>
<mapping class="com.example.litepaltest.Book"></mapping>
</list>
</litepal>
只需要任意一次数据库操作 BookSrore.db数据库可自动创建1
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7Button createDatabase = (Button) findViewById(R.id.create_database);
createDatabase.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Connector.getDatabase();
}
});
- 升级数据库(litepal会自动保存更新前的数据)
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11//Book类
private String press;
public String getPress() {
return press;
}
public void setPrice(double price) {
this.price = price;
}
新建表Category
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22//Category类
public class Category {
private int id;
private String categoryName;
private int categoryCode;
public void setId(int id) {
this.id = id;
}
public void setCategoryName(String categoryName) {
this.categoryName = categoryName;
}
public void setCategoryCode(int categoryCode) {
this.categoryCode = categoryCode;
}
}将Category类映射到模型列表中
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3.使用LitePal添加数据
使Book类继承DataSupport
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3public class Book extends DataSupport{
...
}添加数据
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51Button addData = (Button) findViewById(R.id.add_data);
addData.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Book book = new Book();
book.setName("The Da Vinci Code");
book.setAuthor("Dan Brown");
book.setPages(454);
book.setPrice(16.96);
book.setPress("Unknow");
book.save();//save()由DataSupport继承而来
}
});
```
4.使用LitePal更新数据(1.对已存储（model.isSaved()方法）对象重新设值 2.)
```java
Button updateData = (Button) findViewById(R.id.update_data);
updateData.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Book book = new Book();
book.setName("The Lost Symol");
book.setPrice(10.99);
book.save();
book.setPrice(14.95);//对象重新设值
book.save();
}
})；
```
更巧妙地方法
```java
Button updateData = (Button) findViewById(R.id.update_data);
updateData.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Book book = new Book();
book.setPrice(14.95);
book.setPress("Anchor");
book.updateAll("name = ? and author = ?", "The Lost Symbol", "Dan Brown");
}
});
```
将数据更新成默认值
```java
Book book=new Book();
book.setTofault("page");//setTofault()方法将数据更新成默认值
book.updateAll();
5.使用LitePal删除数据 delete()方法1
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7Button deleteButton = (Button) findViewById(R.id.delete_data);
deleteButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
DataSupport.deleteAll(Book.class, "price < ?", "15");
}
});
6.查询数据 查询API：findALL findFrist findLast1
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14Button queryButton = (Button) findViewById(R.id.query_data);
queryButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
List<Book> books = DataSupport.findAll(Book.class);
for (Book book: books) {
Log.d("MainActivity", "book name is " + book.getName());
Log.d("MainActivity", "book author is " + book.getAuthor());
Log.d("MainActivity", "book pages is " + book.getPages());
Log.d("MainActivity", "book price is " + book.getPrice());
Log.d("MainActivity", "book press is " + book.getPress());
}
}
});
查询API1
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10//select()指定查询哪几列
List<Book>books=DataSupport.select("name","author").find(Book.class);
//where()指定查询约束条件
List<Book>books=DataSupport.where("pages>?","400").find(Book.class);
//order()指定结果排序方式
List<Book>books=DataSupport.order("price desc").find(Book.class);
//limit()查询结果数量
List<Book>books=DataSupport.limit(3).find(Book.class);
//offset()查询结果偏移量
List<Book>books=DataSupport.limit(3).offset().find(Book.class);